I first had Shake Shack inside Citi Field several years ago and I found it delicious. Mind you I'm from San Diego so I'm very familiar with all burger options. Shake shack is not an on the go burger.
I hate to say this but the more I've had it, the more I prefer it to some California chains. The eggy bun is so tasty! Charred beef! Cheese fries! (Although I do prefer fries at other said California chain better). This place is made to order so often food can take some time depending on how busy they are. Also they have a rotating menu among their usuals so that gives you a new experience every time. I need to try their Pie Concrete because the pie mix in comes from a Brooklyn Bakery!
If you want a good sit down experience, have time to chat and watch tv, and want decent burger quality, check this place out with an open mind.
I still like the other place.. and have my cravings for it.. but I've eaten at Shake Shack more often in the last year than other place.